Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$237.31	12.187%	$266.231	$266.23	$266.25	$266.20
Purchase #2	$106.93	8.574%	$116.0982	$116.10	$116.10	$116.10
Purchase #3	$223.90	9.469%	$245.1011	$245.10	$245.10	$245.10
Purchase #4	$181.80	5.539%	$191.8699	$191.87	$191.85	$191.90
Purchase #5	$83.84	7.554%	$90.1733	$90.17	$90.15	$90.20
Purchase #6	$77.99	13.389%	$88.4321	$88.43	$88.45	$88.40
Purchase #7	$133.25	8.791%	$144.964	$144.96	$144.95	$145.00
7 purchase totals =	$1,045.02		$1,142.8696	$1,142.86	$1,142.85	$1,142.90